Under seat servicing advice up/down

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BonBon
Joined: Tue 08 Jan, 2008 21:10
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  Z3 roadster 1.9

Under seat servicing advice up/down

Post by BonBon »

Just got around to doing the seat bushes. Was a lot easier than feared. Each seat took 15 minutes to remove and 30 minutes per rail - where most of the time was cleaning out the crap - the old bush which was non existent. (the 2 online videos were quite helpful)
The bearings on the rails were quite stiff - so I'll give them some lube.
Question: the motor on my up/down (driver's seat) buzzes but the mechanism does not go up and down. Any tips on what to look for/do, so it works when I reassemble?
Seats will be out for a day or two while I re-appholster.
Last edited by BonBon on Tue 29 Apr, 2014 05:41, edited 1 time in total.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
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  Z3 roadster 3.0i
Location: Johannesburg

Re: Under seat servicing advice

Post by Southernboy »

....... I'll be watching the reply to your question... my passenger seat goes fwd / back but not up/down... :wink:
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BonBon
Joined: Tue 08 Jan, 2008 21:10
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  Z3 roadster 1.9

Re: Under seat servicing advice

Post by BonBon »

Here is a pic all in place.
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The only thing that I suspected is the 90 gear drive (aluminum behind black bracket). So I took off the motor and released the "upper" bracket.
The upper bracket turned freely and the gear in the 90 turn was stiff (to be expected).
I also found that the worm going into the 90 drive was turning freely (in pic exposed) - so I turned the gear with a plier and pushed in the worm until the worm caught in the 90 drive. When turning the worm the gear on the exit now also turned.
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Now I expect that it will work for a bit (but I think the 90 gear drive is knackered and the worm will probably pop out of place (it's seat inside the gear is probably worn out).
I don't really care enough to get a battery and test outside the car - so I'll just wait until the seats are back.
If anyone has any insight - I'm game.
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BonBon
Joined: Tue 08 Jan, 2008 21:10
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  Z3 roadster 1.9

Re: Under seat servicing advice

Post by BonBon »

There are also the following possibilities:
1. When I removed the motor the worm slipped out and thus was not engaged. The real problem is that the drive is knackered inside and it cleaves after a few sec of operation.
2. The motor is weak and can't drive the weight. ( I read somewhere ;-) that the motor can be "serviced" - but I think that is only when it stops altogether -I doubt there is a half-way.....or is there?)
3. I counted well over 10 hinges for the up/down. Perhaps friction is too high. It was tight and the mechanism needs a lot of help to get it to move. pic. I lubed it and moved it - but it was still stiff.... It looks like a really small worm and fittings to drive that mechanism with a person on top...
I still suspect the gear drive (worm slipping or drive cleaving).....will also need to decide if I have a go at the motor brushes (even though it works)
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
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  Z3 roadster 3.0i
Location: Johannesburg

Re: Under seat servicing advice up/down

Post by Southernboy »

I trust you disengaged that wormdrive at it's hinge point before attempting to rotate the shaft with those tools?? Looking at the pic you have posted, I would suggest you remove the hinge fixing of the aluminium wormdrive part wich is attached to the shaft you have the tools working on... Turning that shaft whilst the wormdrive is still engaged will be very stiff...
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BonBon
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  Z3 roadster 1.9

Re: Under seat servicing advice up/down

Post by BonBon »

Of course. You can see the nut and bolt are removed from the Al bracket
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Southernboy
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  Z3 roadster 3.0i
Location: Johannesburg

Re: Under seat servicing advice up/down

Post by Southernboy »

Apology... I've never looked under a seat, so really don't know what the layout is down there... Is it possible to dimantle the complete system to properly clean and restore the various hinges ?
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henrycrun
Joined: Wed 18 Apr, 2007 19:48
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  Z3 roadster 1.9
Location: Ely

Re: Under seat servicing advice up/down

Post by henrycrun »

I found it was worth the extra trouble to hook up a 12v supply with the seat out of the car as it identified the problem straight away.

Would a 12v battery charger provide enough current ? - not sure but someone here will know.
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BonBon
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  Z3 roadster 1.9

Re: Under seat servicing advice up/down

Post by BonBon »

Does one just apply -12V or +12V directly to the motor's connector contacts without risk of damage?
BTW - what was your problem? I fear the gear drive mechanism is knackered....
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BonBon
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  Z3 roadster 1.9

Re: Under seat servicing advice up/down

Post by BonBon »

Hate to be defeated...but it's the gear drive and I give up.
I took off the motor and it works fine with +/-12V.
Installed and after a split second the gear just jammed. Motor humming.
As it's a real bitch to get out - I'll just have to live with the seat half way up. :?
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Southernboy
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Re: Under seat servicing advice up/down

Post by Southernboy »

Is the wormdrive faulty ? or the gear which runs on it ??
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BonBon
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Re: Under seat servicing advice up/down

Post by BonBon »

For sure it's the worm drive.
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Southernboy
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Re: Under seat servicing advice up/down

Post by Southernboy »

That's unfortunate..if it had been the gear, it would be easy enough to have one made... :cry:
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BonBon
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Re: Under seat servicing advice up/down

Post by BonBon »

It would not be any better - cuz you'd still need to get inside the 90degree gear housing which looks to be a bitch (otherwise I would have opened it up to have a look)
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Southernboy
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Re: Under seat servicing advice up/down

Post by Southernboy »

It may be worth the effort... I know on my garage door the worm screw is still good after 20 years, but I've needed to replace the gear a couple of times... ie. it seems to be the gear which is the part which wears vs the worm screw...
Is it possible to swap the worm drive unit from one seat to another..ie. to remove just the worm drive and insert it into the "suspect" box, and test if it's the worm or the gear ??
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BonBon
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Re: Under seat servicing advice up/down

Post by BonBon »

TBH - I don't see how to remove it. I looked carefully and it seems that the drive is irreversibly staked with a pipe into the support bracket that is riveted to the rail. :shake:
(and only 2 of the four hex screws in the drive are accessible with the drive still in it's bracket)
Found this on an old post on a US forum Unfortunately BMW decided to mount this gear box in a bracket connected to one of the seat rails. To get it loose you will need to remove the seat "forward reverse" corkscrew in the rail and slide the rail out of the way to access the two pins connecting the gear mechanism.
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Boysie
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Re: Under seat servicing advice up/down

Post by Boysie »

I need to do mine, it always feel a bit daunting, did this problem occur through disturbing the seats ?


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BonBon
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  Z3 roadster 1.9

Re: Under seat servicing advice up/down

Post by BonBon »

I inherited the problem from the previous owner 7 years ago.
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